A conventional gas furnace typically employs several heat exchangers, which form a heating zone to warm an air stream passing through the furnace. An 80% furnace is one where approximately 80% of the energy put into the furnace is converted into heat for the purposes of heating the targeted space. These 80% furnaces include “clamshell” or individual panel halves typically formed by stamping mirror images of the combustion chambers into corresponding metal sheets and coupling them together. The air passes through the heating zone from a blower or fan. These 80% furnaces are also characterized by high operating temperatures, which can cause failure within the heating chamber. As a result, hot spots can occur at certain points in the passageway of the clam shell heat exchanger. The high operating temperatures that create these hot spots can create cracking problems, often referred to as “hot cracks” in the clamshell heat exchanger panels. When such cracks appear, their occurrence is considered a failure of the system. To circumvent these problems, some manufacturers have turned to more expensive sheet metal materials, such as Drawing Quality High Temperature (DQHT) sheet metal materials.